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-   -   Balsa USA 1/3 scale Cub--Which Motor? (https://www.wattflyer.com/forums/showthread.php?t=43542)

trmcrft 02-03-2009 11:22 PM

Balsa USA 1/3 scale Cub--Which Motor?
Getting a Balsa USA 1/3 Cub that I want to go electric for power. Anybody got one? Trying to figure out which motor would be the best choice. My head is spinning from looking at all the possible motors. Ideas please! Thanks!

smokejohnson 02-05-2009 10:58 AM

One things for sure it's gonna be a big motor ;). I would be more worried about the batteries $$$. Are you going to use A123's ?

trmcrft 02-05-2009 11:28 AM

Thanks Smoke, Don't know anything about A123's yet. Just got Lipos figured out(?). $$$ daughters are already gone so can't sell them to finance the batteries. Golf clubs may have to go, don't work anyway. I'm sure the motor may be around 60mm dia and able to turn a 20-22" prop. Waiting for someone to say-'use this one, works for me'.

ENUT 02-10-2009 10:24 PM

I have a couple of questions,Are you building the plane? If so look to lighten the plane as much as possible.web site list 35lbs weight.B-USA planes are exllent aircraft but the wood is on the heavy side.Next you really only have a couple of motor choices,
Actro 60-225 www.hobbyclub.com
Plettenberg www.icare-rc.com
Hacker motors Too. I checked astro flight and didn't see anything that would be enough power.As for the "New Breed of inexpencive motors":rolleyes: I have no clue how good they are.Yes I have read some good news on them ,but you better think about what your building and how much airplane you have involved. My 2cents.

trmcrft 02-10-2009 11:26 PM

Your 2 cents is worth a buck to me and you must be smart if you're from Southington! I go to the Meriden area in Aug for my annual golf trip.
What I'm getting is partially built so I should be able to save some #s. I've been told that 50 watts/lb would do but I am leaning towards 100watts/lb just to have reserve power. My guess is 1.40-1.60 glow equivalent which puts me in the 60mm motor dia area. More thoughts are welcome and thanks, Gino

ENUT 02-11-2009 12:13 AM

Gino,When your talking about this plane remember it has a wing span of 140"!! It aint no sig kadet. Even if you get the plane in the 25lbs range your still looking in the 3000watts neighborhood.Another rule of thumb I use,is I do a static thrust test.This with the plane rtf.You want "AT LEAST 1/3LBS STATIC THRUST"(25lbs=8.5lbs static thrust) I use a simple fishing scale tied to the tail of the plane.Then I floor the throttle,read the scale,check watt meterfor amp draw and check rpm.If these #'s check out the plane has got to fly period!!!


trmcrft 02-11-2009 12:41 AM

ENUT, I got to get my 's' together. On the one hand I said 100w/lb the other hand has been telling me between 2000-2500 watts. Really bad math! I've corresponded with Greg Covey from RCU who is flying a clipped wing 1/3rd Cub on a Axi 5345, and doing aerobatics! That's why I'm asking motor questions now. Getting confusing! And yes, I've been flying small stuff to this point. Your input is appreciated! Gino

trmcrft 02-11-2009 01:38 AM

ENUT, I mis-spoke. The motor was a 7050 on the 1/3 Clipped Wing Cub. Sorry

Greg Covey 03-26-2009 12:55 AM

Hi guys,

I stumbled across this thread so I thought I would set the record straight. The 7050 motor did not work for more than a single flight in my 1/3 scale clipped-wing cub. This was likely due to poor quality.

I ended up using the AXI 5345/16 motor and it continues to perform beautifully! You can read the details of the setup with photos at the end of my build thread link on RCU below.


Matt Kirsch also took some video of it at the 2008 NEAT Fair below.


trmcrft 03-26-2009 02:06 AM

Thanks for checking in Greg! Your input has been a great help to me. Gino

PMcIntire 03-27-2009 06:57 AM

Figuring out the A123's takes less than the lipos, you just might need more cells. The other electric r/c site has some nice details on the A123, I bookmarked this post when I considered them for a project. They are slightly heavier, and slightly more expensive, but they last a very long time, under more intense situations. You lose your plane, you will not lose that battery pack, and you can almost be guaranteed 400 flights without a hitch (barring any maintennace issues). You can charge them in far less time (15 minutes) than you may be spending in the air... It's just the way to go, especially in your case since you are not required to aim for something like 200-400 watts per pound, or weight critical for that matter.


While this may be sacrilege, (unless the weight is that critical) you may consider using NiMH packs for your project. (They will not charge as fast as the A123's) The latest batch of sub-C cells used in R/C cars are at 4600 (IB4600). I just saw 5300mAh for another cell. Electric flight has ignored NiMH and NiCd since polymers came out.
Tanic packs makes A123 packs you will likely use. Aim for 2P to 4P if you want to fly a decent amount of time. Are you goung to aim for the same power level as Greg Covey has? Probably around 14S A123, or 40 cells NiMH? You're looking at around $700 for the pack in A123 (14S1P) at about 2.2lb, and If I am right at $6 a cell for the IB4600, $280 per pack at about 6.5 pounds. be careful when you see tenergy as the A123 brand. There is A123, and then there is tenergy which appears to have copied the A123 and cell designation. They are not the same. Tenergy has been used with success, but you must check that you are using the correct cells.

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